Prior art gripper devices for gripping pipes are used for handling pipes and similar objects in an automated manner. The conventional such gripper device may, for example, be arranged on a robot arm that is used for reorienting the pipe from a horizontal position to a vertical position. In regards to the petroleum industry, the pipes are, for example, drilling pipes, where a plurality of drilling pipes are to be connected with each other for the drilling operation. During such operation, pipes of different diameters are to be firmly gripped, reoriented and securely connected with each other.
A problem with prior art gripper devices for such operation is that they are extensive in size. In the petroleum industry, and in particularly offshore operations, the available space on a drilling rig is limited. Yet, to be able to selectively pick pipes from a storage rack, the pipes must be sufficiently spaced apart for the gripper device.
A further problem with prior art gripper devices is to enable pipes with different diameters and having irregularities, such as various degree of ovality, to be securely gripped with substantially the same contact pressure on both gripping arms and while allowing the pipes to be rotated around their longitudinal axes.
WO 2011/021943 discloses a gripper adapted for gripping petroleum pipes of different diameters. The gripper comprises two gripper arms movably supported in a gripper housing. The gripper arms are connected to the housing via a pair of pivotal link arms and a pair of pivotal drive arms. The drive arms are actively driven by means of a pair of rotatable shafts supported in the gripper housing. The geometry of the gripper arms and the link and drive arms, and in particular, the different lengths of the link and drive arms, enables the gripper to grip pipes within a range of different diameters. However, the arrangement of the two rotatable drive shafts spaced apart from each other prevents a compact design of the gripper.
U.S. Pat. No. 4,858,979 discloses a gripper device comprising two harmonic drive transmissions arranged spaced apart in series on a drive shaft. While the gripper device employs a single drive shaft, the two transmissions spaced apart from each other are likewise preventing a compact design of the gripper device.